In the prior art, these kinds of expansion valves were used in refrigeration cycles of air conditioners in automobiles and the like. FIG. 9 shows a prior art expansion valve in cross-section together with an explanatory view of the refrigeration cycle. The expansion valve 10 includes a valve body 30 formed of prismatic-shaped aluminum comprising a refrigerant duct 11 of the refrigeration cycle having a first path 32 and a second path 34, the one path placed above the other with a distance inbetween. The first path 32 is for a liquid-phase refrigerant passing through a refrigerant exit of a condenser 5 through a receiver 6 to a refrigerant entrance of an evaporator 8. Tile second path 34 is for a liquid-phase refrigerant passing through the refrigerant exit of the evaporator 8 toward a refrigerant entrance of a compressor 4.
An orifice 32a for the adiabatic expansion of the liquid refrigerant supplied from the refrigerant exit of the receiver 6 is formed on the first path 32, and the first path 32 is connected to the entrance of the evaporator 8 via the orifice 32a and a path 321. The orifice 32a has a center line extending along the longitudinal axis of the valve body 30. A valve seat is formed on the entrance of the orifice 32a, and a valve means 32b supported by a valve member 32c and forming a valve structure together with the valve seat is included thereto. The valve means 32b and the valve member 32c are welded and fixed together. The valve member 32c is fixed onto the valve means 32b and is also forced by a spring means 32d, for example, a compression coil spring.
The first path 32 where the liquid refrigerant from receiver 6 is introduced is a path of the liquid refrigerant, and is equipped with an entrance port 321 and a valve room 35 connected thereto. The valve room 35 is a room with a floor portion formed on the same axis of the center line of the orifice 32a, and is sealed by a plug 39.
Further, in order to supply drive force to the valve body 32b according to an exit temperature of the evaporator 8, a small hole 37 and a large hole 38 having a greater diameter than the small hole 37 are formed on said center line axis perforating through the second path 34. A screw hole 361 for fixing a power element member 36 working as a heat sensor is formed on the upper end of the valve body 30.
The power element member 36 is comprised of a stainless steel diaphragm 36a, an upper cover 36d and a lower cover 36h each defining an upper pressure activate chamber 36b and a lower pressure activate chamber 36c divided by said diaphragm and forming two sealed chambers above and under the diaphragm 36a, and a tube 36i for enclosing a predetermined refrigerant working as a diaphragm driver liquid into said upper pressure activate chamber, and is fixed to the valve body 30 by a screw 361. Said lower pressure activate chamber 36c is connected to said second path 34 via a pressure hole 36e formed to have the same center as the center line axis of the orifice 32a. A refrigerant vapor from the evaporator 8 is flown through the second path 34. The second path 34 is a path for gas phase refrigerant, and the pressure of said refrigerant vapor is added to said lower pressure activate chamber 36c via the pressure hole 36e.
Further, inside the lower pressure activate chamber 36c is a heat sensing shaft 36f made of aluminum and an activating shaft 37f made of stainless steel. Tile heat sensing shaft 36f exposed horizontally inside the second path 34 is movably positioned through the second path 34 inside the large hole 38 and contacts the diaphragm 36a so as to transmit the refrigerant exit temperature of the evaporator 8 to the lower pressure activate chamber 36c, and to provide a driving force in response to the displacement of the diaphragm 36a according to the pressure difference between the upper pressure activate chamber 36b and the lower pressure activate chamber 36c by moving inside the large hole 38. The activating shaft 37f is movably positioned inside the small hole 37 and provides pressure to the valve means 32b against the spring force of the spring means 32d according to the displacement of the heat sensing shaft 36f. The heat sensing shaft 36f comprises a stopper portion 312 having a large radius and works as a receiving member of the diaphragm 36a, the diaphragm 36a positioned to contact its surface, a large radius portion 314 contacting the lower surface of the stopper portion 312 at one end surface and being moveably inserted inside the lower pressure activate chamber 36c, and a heat sensing portion 318 contacting the other end surface of said large radius portion 314 at one end surface and having the other end surface connected to the activating shaft 37f.
Further, the heat sensing shaft 36f is equipped with an annular sealing member, for example, an o-ring 36g, for securing the seal of the first path 32 and the second path 34. The heat sensing shaft 36f and the activating shaft 37f are positioned so as to contact each other, and activating shaft 37f also contacts the valve means 32b. The heat sensing shaft 36f and the activating shaft 37f form a valve driving shaft together. Therefore, the valve driving shaft extending from the lower surface of the diaphragm 36a to the orifice 32a of the first path 32 is positioned having the same center axis in the pressure hole 36e.
Further, the heat sensing shaft 36f and the activating shaft 37f could be formed as one, with the heat sensing shaft 36f being extended so as to contact the valve means 32b. Still further, a plug body could be used instead of the tube 36i for sealing the predetermined refrigerant.
A known diaphragm driving liquid is filled inside the upper pressure activating chamber 36b placed above a pressure activate housing 36d, and the heat of the refrigerant vapor from the refrigerant exit of the evaporator 8 flowing through the second path 34 via the diaphragm 36a is transmitted to the diaphragm driving liquid.
The diaphragm driving liquid inside the upper pressure activate chamber 36b adds pressure to the upper surface of the diaphragm 36a by turning into gas in correspondence to said heat transmitted thereto. Tile diaphragm 36a is displaced in the upper and lower direction according to the difference between the pressure of the diaphragm driving gas added to the upper surface thereto and the pressure added to the lower surface thereto.
The displacement of the center portion of the diaphragm 36a to the upper and lower directions is transmitted to the valve member 32b via the valve member driving shaft and moves the valve member 32b close to or away from the valve seat of the orifice 32a. As a result, the rifrigerant flow rate is controlled.
That is, the gas phase refrigerant temperature of the exit side of the evaporator 8 is transmitted to the upper pressure activate chamber 36b, and according to said temperature, the pressure inside the upper pressure activate chamber 36b changes, and the exit temperature of the evaporator 8 rises. When the heat load of the evaporator rises, the pressure inside the upper pressure activate chamber 36b rises, and accordingly, the heat sensing shaft 36f or valve member driving shaft is moved to the downward direction and pushes down the valve means 32b via the activating shaft 37, resulting in a wider opening of the orifice 32a. This increases the supply rate of the refrigerant to the evaporator, and lowers the temperature of the evaporator 8. In reverse, when the exit temperature of the evaporator 8 decreases and the heat load of the evaporator decreases, the valve means 32b is driven in the opposite direction, resulting in a smaller opening of the orifice 32a. The supply rate of the refrigerant to the evaporator decreases, and the temperature of the evaporator 8 rises.
In a refrigeration system using such an expansion valve, a so-called hunting phenomenon occurs wherein over supply and under supply of the refrigerant to the evaporator repeats in a short term. This happens when the expansion valve is influenced by the environment temperature, and, for example, the non-evaporated liquid refrigerant is adhered to the heat sensing shaft of the expansion valve. This is sensed as a temperature change, and the change of heat load of the evaporator occurs, resulting in an oversensitive valve movement.
When such hunting phenomenon occurs, it not only decreases the ability of the refrigeration system as a whole, but also affects the compressor by the return of liquid to said compressor.
The object of the present invention is to provide a cost effective expansion valve that avoids the occurrence of the hunting phenomenon in the refrigeration system with only a simple change in structure.